1. Field of the Invention
The present invention is in the field of cathode ray tubes with an improved implosion protection device.
2. Description of the Prior Art
The tube envelope of a cathode ray tube is compressed inwardly by atmospheric pressure so that when it is broken by an external shock or the like, the tube envelope is cracked into pieces and the pieces may be scattered substantially by the explosion. In order to prevent such an occurrence, prior art, as shown in FIG. 1 provides a tube envelope 1 which is reinforced near its panel portion, the weak point from a structural standpoint, by an anti-explosion band made of metal.
In a color cathode ray tube, a magnetic field may affect the electron beam to change its path so that the color purity of the color cathode ray tube is deteriorated. To avoid this effect, as shown in FIG. 1, the tube envelope 1 may be partly covered with an external magnetic shield member 6, to which there may be attached a degaussing coil 4. An alternating, attenuating current is flowed through the degaussing coil 4 and the current passing therethrough is gradually decreased to carry out the degaussing operation. The external magnetic shield member 6 is secured to the tube envelope 1 as follows. The external magnetic shield member 6 is inserted to cover the tube envelope from its neck-down portion and then is secured to the cabinet (not shown) together with the anti-explosion band by screws at attaching portions 5.
Alternatively, after the external magnetic shield member 6 is assembled to the cabinet, the tube envelope 1 is inserted therein and then the attaching portions 5 of the anti-explosion band mounted on the tube envelope are secured to the cabinet by means of screws.
The above described conventional cathode ray tube has an anti-explosion function and means for decreasing the influence of external magnetic fields, but it would be desirable if the number of assembly parts would be decreased, so that the number of manufacturing process steps and the manufacturing costs thereof could be reduced.